Airlines must choose carefully which parts of merged brands to hold on to

750 liters of paint needed to respray a Boeing 777

(CNN) -- The designs painted on planes help distinguish one airline from another, using colors that promote and represent the brands.

But with frequent mergers and acquisitions in the industry over recent years, traffic in and out of paint shops has increased to keep planes updated with new airline identities.

The latest to emerge from a respray, covering the remnants of bankruptcy, is American Airlines.

US Airways and American Airlines will form the largest airline in the world by passenger numbers, worth an estimated $11 billion. The new company will retain the American Airlines name, but it will have up to 73 aircraft repainted by the end of this year to reflect its new branding.

The former look of its planes features a silver, bare-metal finish with a red, white and blue stripe running along the body, its iconic logo of an eagle and double A adorning the tailfins. The new design covers the planes in silver paint and puts stripes on the tail.

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"It brings American into the Apple age with its nice reflective coating," says Sudeep Ghai, a strategist with Athena Aviation, and airline management consulting firm.

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"I think where there are challenges are perhaps some of the brand mark elements that have been left behind, which have been around for 40 years," Ghai says, referring to the airline's logo, which has been radically changed.

In recent years, the six major U.S. carriers have consolidated into three. Northwest Airlines was completely absorbed when it merged with Delta in 2008. Two years later, Continental merged with United.

With each merger, airlines must choose carefully which parts of brands to hold onto. In the case of Continental and United, the newly formed company kept Continental's distinctive logo of a yellow globe.

"They did a very sensible thing, actually. They retained the United name -- the more recognized name worldwide -- with the Continental logo," says Willie Walsh, the CEO of International Airlines Group, the parent company of British Airways. "And I think that was meant to bring the Continental people into the business. There's a sense of inclusiveness, which I think was a smart move."

There are instances of companies getting the rebranding wrong, Walsh says, like the unpopular tailfin designs on British Airways planes in the late 1990s. "But out of that came something fantastic: the Chatham flag, the livery that we have on our aircraft today," he says.

I think we'll see more consolidation, and I think the industry recognizes that it is a positive development.Willie Walsh, CEO of International Airlines Group

Acquisitions and the new coats of paint that often follow have been cropping up across Europe, too. After IAG bought the airline British Midland International from Lufthansa last year, dozens of BMI's planes needed to be repainted to reflect its new branding, a process that used around 750 liters of spray paint per plane.

Meanwhile, Lufthansa is getting ready to relaunch Germanwings, a low-cost airline that it acquired in 2009. Part of the preparations involves repainting the fleet in the new Germanwings livery, which incorporates colors that signify Lufthansa's ownership.

"We decided we needed a fresh approach. And what you see in our new livery is Lufthansa's yellow colors and our raspberry colors," says Thomas Winkelmann, the CEO of Germanwings.

And passengers can expect more fresh paint jobs ahead, as the flailing airline industry continues to see mergers as a way to strengthen businesses.

"It happens on a slow-drip basis," Walsh said, "but I think we'll see more consolidation, and I think the industry recognizes that it is a positive development."